Distorted mp3 playback on MAX98357A

[bbtinkerer]

CircuitPython version and board name

Adafruit CircuitPython 9.2.6 on 2025-03-23; Raspberry Pi Pico 2 with rp2350a
Board ID:raspberry_pi_pico2

same issue when using Pi Pico rp2040

Code/REPL

# sample code and mp3 from https://learn.adafruit.com/mp3-playback-rp2040/pico-i2s-mp3
#
# SPDX-FileCopyrightText: 2021 Kattni Rembor for Adafruit Industries
#
# SPDX-License-Identifier: MIT

"""
CircuitPython I2S MP3 playback example.
Plays a single MP3 once.
"""
import board
import audiomp3
import audiobusio

audio = audiobusio.I2SOut(board.GP0, board.GP1, board.GP2)

mp3 = audiomp3.MP3Decoder(open("slow.mp3", "rb"))

audio.play(mp3)
while audio.playing:
    pass

print("Done playing!")

Behavior

Audio playback of mp3s are distorted when playing back using a MAX98357A.

Description

Distorted playback also with CircuitPython 9.2.5 on both Pi Pico with rp2040 and Pi Pico 2 rp2350

Additional information

Tried using audiomixer to lower volume since audio sounded like a high gain was applied to it, but that only lowered the volume, the audio was still distorted.

MP3s play fine when using CircuitPython 9.2.4 and earlier.

[bablokb]

I can confirm this behavior using a PCM5102 and a Pico2-W. So this is not related to the specific I2S-amp chip MAX98357A.

[bablokb]

It is not related to the Pico, I have the same issue with an ESP32-S3

[jepler]

I reproduced the same/similar issue on pygamer. Through git bisect, I narrowed it down to e15eba0 (#10036).

I'll investigate further & hopefully make a fix.

[bablokb]

PR #10185 fixes it for me. Tested with a Pico2-W and PCM5102.

Thanks!

[jepler]

thanks for testing @bablokb !

[dhalbert]

Fixed by #10185.